1. Field of the Invention
The invention relates to a method and apparatus for the running and setting of, and to the unlatching from and relatching to, a tubing hanger assembly in a subterranean well, the hanger when in anchored position carrying the weight load of production tubing extending therebelow and receiving through its uppermost end production tubing extending thereabove to the surface of the well. The tubing extending from the surface of the well normally will carry one or more safety valves and is run in the well together with the tubing hanger assembly and the tubing extended therebelow. The hanger may be run and anchored in the well on and with the upper tubing containing the safety valves in one trip.
2. Description of the Prior Art
In the production of well fluids, such as oil and/or gas, from wells, it has been the practice to provide automatically closeable shut-off or safety valves which are located downhole in the well and are held open by control fluid pressure, the valves closing automatically when control fluid pressure is purposely reduced to allow the valves to close or damage occurs to the control fluid system at the well head or on an offshore platform. Such valves are employed below the well head, and in the case of offshore wells, the valves are installed below the mud line at such depth as may be desired or established by regulation, so that in the event of damage of the well caused by shifting earth or subsidence, or well head catastrophe, the well can be shut in to avoid loss of valuable well fluids into the water, and also, to avoid contamination of the water and the shore.
Many offshore wells are produced from spaced well zones through separate strings of production tubing, and a safety or shut-off valve is required for each zone. Since, from time-to-time, it is necessary to perform various remedial operations through the tubing strings, it is preferred that the safety valves be easily removed from the well for service or repair. Accordingly, commercially available safety or shut-off valves have been provided which have been run into the well casing on production tubing and landed in a tubing hanger which supports the greater weight of the downwardly extending production tubing strings. Typically, such a tubing hanger has been run into the well casing on a setting tool to a desired location, and, in the case of an offshore well, to a prescribed depth below the mud line. In such an apparatus, the tubing hanger is anchored in the well casing and the setting tool is released from the tubing hanger and removed from the well. The tubing hanger provides a seat for the safety or shut-off valve assembly which is run into the well on an upward extension of the production tubing and landed in the tubing hanger, subsequent to the setting of the hanger and retrieval of the hanger setting tool.
Typical of such prior art apparatuses is that as disclosed in U.S. Pat. No. 3,771,603, issued Nov. 13, 1973, entitled "Dual Safety Valve Method And Apparatus", to Talmadge L. Crowe, the disclosure of which is hereby incorporated herein by reference. The necessity of two trips into the hole with work strings and/or other means to first carry and anchoringly set the tubing hanger and thereafter land the conduits containing the safety valves therein is an economic deterrent since considerable rig time is expended in running a first work string and/or other means for anchoring the hanger, retrieving the work string and/or other means, and thereafter running the production tubing containing the safety valve or valves into sealing engagement with the hanger.
The present invention obviates many of the problems typified by prior art, commercially available apparatuses, and is an improvement thereto by providing means for setting of the tubing hanger and sealing engagement of the production tubing containing the safety valve or valves in only one trip, thus eliminating the need for costly retrieval of the initial setting work string and/or other means and thereafter running into the well the production tubing containing the safety valves for sealing engagement with the tubing hanger.
Although the present invention finds particular adaptability for use in multi-zone completions, wherein two or more production tubing strings extend from the top of the well through the tubing hanger apparatus, it is easily adaptable for use with only one production tubing string in a completion of a well containing only a single production zone.
When the invention is utilized in conjunction with multiproduction tubing strings, it is particularly unique inasmuch as a single latch assembly may be utilized, as described below, in one embodiment, to engage the upper tubing string section extending from the surface of the well into sealing engagement with the tubing hanger. Hertofore, some prior art apparatuses have utilized dual latch assemblies. The provision of a single latch assembly is particularly beneficial because it can carry substantially the complete weight of the production tubing therebelow and thus can accomplish whatever the weight load strength of the production tubing therebelow can accomplish, thus enabling the tubing hanger to carry the load that is equal to the strength of the dual production tubing strings. This ability also is made possible by utilization of a unique shear-out safety joint apparatus which provides a means of separating the tubing conduit above the safety valve means when a predetermined load across the shear-out safety joint is exceeded, and also provides a bridge so that a weight load up to the full production tubing strength initially can be carried for a preliminary operation. such as the setting of a packer apparatus below the hanger assembly. Thereafter, the bridge may be removed and the load capability of the shear-out safety joint apparatus is relaxed.
The tubing hanger apparatus incorporates means for hydraulically releasing the latch assembly for retrieval of the production tubing string extending to the top of the well which has been initially sealingly landed within the tubing hanger. The latch assembly also has auxiliary mechanical disengaging means which may be activated in the event of failure of the latch assembly to disengage from the tubing hanger by hydraulic means.
In an alternative embodiment, the latch assembly also incorporates hydraulic means for setting of the tubing hanger to anchor the hanger to the well casing. Thus, the tubing hanger may be set hydraulically without the use of a wireline activated or other separate setting tool.
Each component part of the tubing hanger assembly is designed with rotational torque capability to accommodate the mechanical release backup feature of the latch apparatus.
The single trip tubing hanger assembly of the present invention also enables the pulling and repair of the tubing strings sealingly latched in the tubing hanger to seal failure, nipple damage, or the like, without the retrieval of the entire string of production tubing, the string of production tubing below the tubing hanger remaining in the well after retrieval of the production tubing section extending from the top of the well and initially sealingly engaged within the tubing hanger and carrying the safety valve means. The retrieval of the production tubing extending from the top of the well to the tubing hanger (hereinafter sometimes referred to as the "space-out section") may be accomplished by use of only a small crane, as opposed to the prior art utilization of a large drilling rig, or the like.
The mechanical release backup feature of the latch assembly alternatively incorporates a swivel sub apparatus which permits rotation of the section of production tubing immediately above the tubing hanger when the space-out section is secured against rotation into the surface hanger at the top of the well, or fixed by its position in the space-out assembly.